Embodiments of the present invention generally relate to methods and apparatus for locating and classifying optical radiation. More specifically, the present invention relates to methods and apparatus for locating and classifying optical radiation in which a plurality of gratings and/or detectors are orthogonally oriented to increase the accuracy of such location and/or classification.
Systems and methods are known in the art for radiation detection and/or classification. One such system is a hyperspectral system that collects information concurrently from a plurality of adjacent infrared spectral bands. A collector system includes an optical train for receiving the incoming radiation, a disperser for separating the received infrared radiation into multiple adjacent bands of interest, and a focal plane array for detecting the individual infrared bands and producing corresponding output signals. The focal plane array in this collector system is an enhanced quantum well infrared photodetector having multiple physical dimensions of each detector varied in a predetermined manner to alter the frequency of responsivity of the detector to form the multi-band pixels of the received image. Consequently, the generated output signals may be processed to review selected bands of interest or to determine if certain types of targets are present based upon the received radiation.
In another similar system, a multi-spectral detector is used to identify objects in a specific field of view. The multi-spectral detection system includes an optically dispersive element, a detector array, and an integrated circuit. The optically dispersive elements separates laser detection and ranging (“LADAR”) radiation or other radiation received from a scene into a plurality of spectral components and distributes the separated spectral components to a detector array. The detector array includes a plurality of individual detectors capable of detecting the spectral components of the LADAR and scene radiation. The integrated circuit is coupled to the detector array and is capable of generating a plurality of electrical signals representative of predetermined characteristics of the detected radiation. In one use of this detector, LADAR is actively detected while scene radiation is passively detected.
In yet another similar system, a spectral detector is designed with a multi-waveband focal plane array and high efficiency gratings capable of dispersing all spectral orders with high efficiency. The high efficiency of the gratings is achieved by varying the blaze of the gratings. Radiation received by the detector passes through the high efficiency gratings prior to striking the focal plane array. This system allows spectra corresponding to overlapping grating orders to be focused onto the focal plane array to create spectral images of a scene simultaneously in multiple wavelength regions. Such detectors allow detection of spectral ranges having several octaves of wavelength while minimizing the size and cryogenic requirements of the detector.
A similar high-sensitivity multispectral sensor is also known for improving sensing in airborne hyperspectral and multispectral sensing applications such as thermal or infrared military target detection and/or identification. This sensor combines dispersive spectrometer techniques, such as those discussed above, with filtered time-delay-integrate (“TDI”) detector techniques to provide improved noise equivalent spectral radiance (“NESR”) by increasing dwell time, interband temporal simultaneity, and spatial registration. This sensor includes hyperspectral, multispectral, and dual-band arrangements.